The present invention generally relates to capsules for containing beverage ingredients, to a beverage producing system for use in connection with such capsules as well as to methods for producing beverages on the basis of ingredients contained in such capsules.
The background of the present invention is the field of capsules which contain beverage or other comestible (e.g. soup) ingredients. By means of an interaction of these ingredients with a liquid, a beverage or other comestibles, such as for example soups, can be produced. The interaction can be for example an extraction, brewing, dissolution, etc. process. Such a capsule is particularly adapted to contain ground coffee in order to produce a coffee beverage by having hot water under pressure enter the capsule and draining a coffee beverage from the capsule.
FR 1537031 does not show separated capsules, but a blister pack containing coffee powder. As two foil members are sealed together at the top foil member in an area between two adjacent compartments, these compartments can not be separated from each other without loosing the tight seal between the foil members. A filter is arranged at the bottom of each compartment and thus opposite of the area where the two foil members are sealed. The outlet side of the compartment is opened by actively moving a perforation member, via a spring force, against the lower face of the compartment. Due to the blister pack technology the top face of the compartments has to be flat.
Also according to CH605293 a filter is, at its rim portion, sandwiched between the foil member and the capsule base body wall. The foil member is additionally provided with a weakened area and is not designed to be perforated by being thrust against a relief plate. The filter is used as a screen to avoid coffee grains from being delivered in the liquid.
EP0507905B1 relates to an apparatus and cartridge for preparing a liquid product. An internal filtering membrane is placed in the bottom of the cartridge for retaining solid particles in the cartridge and prevent clogging of the flow channels provided in the perforating members.
EP-A-512468 relates to a capsule for the preparation of a beverage wherein a filter paper is welded between the peripheral area of the cup and the tearable membrane. The filter paper is used only to ensure no coffee grains can exit the membrane when torn.
US2006/0236871A1 relates to a single portion cartridge which is suitable in particular for brewing a portion of a coffee beverage wherein a distributing and/or supporting structure is provided with at least one opening which is covered by a textile fabric forming a screen between the enclosure and the large outlet. The essential object of this invention is to minimize the escape of particles of the beverage substance from the cartridge during the brewing operation because a large opening is made in the bottom of the capsule body and the particles would be washed out in absence of such distributing structure. The textile fabric has a pore size in the range from 10 to 500 microns, preferably from 30 to 150 microns.
Systems and methods for obtaining fluid comestibles from substances containing isolated capsules are for example known from EP-A-512470 (counterpart of U.S. Pat. No. 5,402,707).
The capsule 200 as shown in FIG. 1 has a frustoconically-shaped cup which may be filled e.g. with roasted and ground coffee 300 and which is closed by a foil-like tear face cover 400 welded and/or crimped to a flange-like rim 140 which extends laterally from the side-wall of cup. A capsule holder 130 comprises a flow grid 120 with relief surface element members.
The capsule holder 130 can be accommodated in a larger support 150 which has a lateral wall 240 and a beverage outlet 270 for the passage of extracted coffee beverage.
As can be seen from FIG. 1 the extraction system further comprises a water injector 700 having water inlet channel(s) 201 and an annular element 800 with an internal recess of which the shape substantially corresponds to the outer shape of the capsule. On its outer part, the annular member 800 comprises a spring 220 holding a ring 230 for releasing the capsule on completion of extraction.
In operation, a capsule 200 is placed on the capsule holder 130. The water injector 700 perforates the upper face of the cup. The lower tear face 400 of the capsule rests on the radially arranged members of the capsule holder 130.
The water is injected through the channel 201 of the water injector 700 and impinges on the bed 300 of coffee. The pressure in the capsule increases and the tear face 400 increasingly follows the shape of the radial opening relief members. Such radial opening relief members could be replaced by pyramid-shaped reliefs or other shapes of relief. When the constituent material of the tear face reaches its breaking stress, the tear face tears along the relief members. The extracted coffee flows through the orifices of the flow grid 120 and is recovered in a container (not shown) beneath the beverage outlet 270.
The principles of this extraction process as far as it can be maintained in connection with the present invention can be summarized as follows:                An initially gastightly sealed capsule is inserted in capsule holder means.        The capsule holder means is then introduced associated to the water injection means of the machine such that an annular element surrounds the sealed capsule. In a first wall of the capsule at least one opening is generated.        Water entering the capsule through the opening in the first wall is interacting with the ingredients contained in the capsule while traversing the interior of the ingredient contained in the capsule and is then made to leave the capsule through at least one opening/perforation created in the second wall under the effect of the pressure building up in the capsule.        
The perforations in the second face, especially when cooperating with the relief members, filter the beverage leaving the interior of the capsule so that non-soluble coffee particles remain in the capsule. It has been considered in the prior art that such filtering is sufficient (see e.g. column 4 of EP512470B1).
EP 512468B1 teaches to have a capsule with a flat perforable foil member for delivery of the coffee. A filter paper can be sealed between the foil member and the rim of the base body. The capsule, i.e., the membrane opens under the sole effect of the pressure in the capsule.
Also according to CH605293 a filter is, at its rim portion, sandwiched between the foil member and the capsule base body wall. The foil member is additionally provided with a weakened area and is not designed to be perforated by being thrust against a relief plate.
The invention has found that, according to the teaching of the prior art, when a sealed gastight capsule with a simple perforable foil member is placed against a capsule holder with a multitude of small reliefs, and in particular, small squared or rectangular perforation elements, one may have the following problems:                The extraction process may be slowed down, in particular for capsules containing a larger dose of coffee designed for delivering coffee beverages,        The extraction process may flow at inconsistent flow times from one capsule to another,        The extraction is not clean enough and coffee particles can escape the capsule through the small perforations created through the foil member after extraction, when the capsule is removed from the machine in particular, due to the presence of fine grinding outside the typical range designed for the current system (e.g., below an average grind size of 200 microns).        
These problems are targeted at by the present invention and is remedied by means of the features of the independent claims. The dependent claims further develop the central idea of the invention.